Open CSV/JSON/Vega Lite/Voyager file from the file browser or existing window

[saulshanabrook]

A user should be able to open a variety of formats from the file browser or from an existing view of that file in Voyager. These include:

• Tabular data files likes CSV/TSV or JSON format supported by Vega Lite/voyager, which should open in Voyager with with no Specified View.
• Vega Lite files (.vl/.vl.json), which should open with the existing specification as the Specified View.
• Voyager saved redux state files(.vy.json), which should restore the Voyager state to that.